Submitted to: ARS Food Safety and Inspection Service Research Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 12/13/1995
Publication Date: N/A
Technical Abstract: A national study of health and management of cattle in feedlots was conducted. Fifty fecal samples were collected from 100 feedlots. Within each feedlot, 25 fresh fecal samples were collected from each of the pen floors of cattle which had been on feed the shortest and the longest period of time. Samples were cultured for the presence of Salmonella spp. in both htetrathionate broth (Tet) and GN Hajna broth (GN). After incubation for 4 h (Tet) or 24 h (GN), both Tet and GN were transferred to Rappaport medium (R-10), incubated overnight, then streaked onto brilliant green agar with sulfadiazine plates (BGS). Tet cultures were also struck onto BGS after 48 h incubation. All incubation temperatures were 37 deg C. Presumptive positive colonies were characterized by biochemical tests then serotyped at the National Veterinary Services Laboratories. The total number of samples collected was 4,977; 2,484; and 2,495 from the shortest and longest on feed, respectively. Salmonella spp. were recovered from 38% (38/100) of the feedlots. Salmonella spp. were recovered from 5.5% (273/4,977) of all samples and from 3.5% (88/2,484) and 7.4% (185/2,495) of samples from cattle shortest and longest on feed, respectively. The most common serotype recovered was S. anatum (27.9%), followed by S. montevideo (12.9%), S. muenster (11.8%), S. kentucky (8.2%), and S. newington (4.3%). The most common serogroups identified were E1 (39.6%), C1 (20.7%), and B (10.4%). Shedding of the most common serotypes associated with human illness occurs infrequently (13/273;4.8%). Of the positive isolates, 77.3% were recovered following culture in both Tet and R-10 while only 49.8% and 36.6% were recovered in Tet alone or GN and R-10, respectively. This study may serve as baseline information for future studies.